PATHOGENICITY OF PLAGUE BACILLUS 397 



sometimes a discharge from the eyes, and towards the 

 end, staring coat and perhaps convulsive and paralytic 

 attacks. The post-mortem appearances are extensive 

 haemorrhagic oedema at the seat of inoculation, enlarge- 

 ment and congestion of the spleen, and enlargement of, 

 and hemorrhages into, the inguinal and axillary lymphatic 

 glands. If the animal live six or seven days, the glands 

 may be as large as small nuts (see some admirable prepara- 

 tions in the College of Surgeons Museum). The spleen 



FIG. 45. Spleen of guinea-pig inoculated with plague. 

 (Nat. size.) 



may be enormous, six times its natural size, and studded 

 with small yellowish nodules resembling miliary tubercles, 

 consisting of necrotic areas with masses of bacilli (Fig. 45) ; 

 the lungs also may be more or less inflamed, and contain 

 small and large necrotic foci. The bacilli are extremely 

 numerous at the seat of inoculation, in the glands, and 

 in the spleen, less so in the peritoneal fluid, liver, and 

 blood ; if the death of the animal is delayed the exudation 

 in the bronchi may contain considerable numbers. Some 

 bacilli may generally be found in the duodenum, trachea, 

 and larynx. Mice usually die in from two to three days, 

 and rats in from three to seven days after inoculation. In 

 rats and mice the post-mortem appearances are similar 

 to those in the guinea-pig. A very small dose of a pure 

 culture may fail to kill an inoculated animal. Rabbits 

 are much less susceptible to plague than guinea-pigs, and 

 may be injected with considerable doses of living cultures 

 without showing marked illness. Rats can be infected 



